Gas-phase photocatalytic oxidation of refractory VOCs mixtures: Through the net of process limitations

Abstract

Photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) presents an effective means of indoors air treatment. Shortcomings, however, include relatively low oxidation rate, sometimes formation of toxic by-products and catalyst deactivation. These obstacles are to be surmounted via synthesis of active catalytic materials and efficient catalyst regeneration at properly chosen process parameters. The article describes the photocatalytic performance of a novel flame aerosol synthesised nano-structured titania F3 and the method of accelerated photocatalyst activity restoration using small amounts of ozone. The experimental research into PCO abating VOCs in mixtures was undertaken following the performance of F3 compared to the benchmarking commercially available photocatalyst P25. The mixture containing acrylic acid, acrylonitrile and toluene was degraded at F3 and P25 photocatalysts, whereas the mixture of acrylonitrile, styrene and toluene—at P25 with admixtures of ozone; ozone was also used for regeneration of P25. The contact time, VOCs and ozone concentration in mixtures, temperature, and air humidity varied. In the experimental conditions, the novel photocatalyst showed activity substantially surpassing the one of the benchmark: within the experimental conditions, F3, contrary to P25, showed no symptoms of deactivation, emitting only trace amounts of toxic HCN product. The novel photocatalyst thus confirmed its promising efficiency in abatement of VOCs mixtures. Ozone appeared to be effective aid in both PCO of VOCs and the photocatalyst activity restoration dramatically shortening the photocatalyst regeneration time.